SOURCE

//定义画布宽高和生成点的个数
	var WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 5;
	
	var canvas = document.getElementById('Mycanvas');
	canvas.width = WIDTH,
	canvas.height = HEIGHT;
	var context = canvas.getContext('2d');
	context.strokeStyle = 'rgba(0,0,0,0.1)',
	context.strokeWidth = 1,
	context.fillStyle = 'rgba(0,0,0,0.2)';
	var circleArr = [];

	//线条：开始xy坐标，结束xy坐标，线条透明度
	function Line (x, y, _x, _y, o) {
		this.beginX = x,
		this.beginY = y,
		this.closeX = _x,
		this.closeY = _y,
		this.o = o;
	}
	//点：圆心xy坐标，半径，每帧移动xy的距离
	function Circle (x, y, r, moveX, moveY) {
		this.x = x,
		this.y = y,
		this.r = r,
		this.moveX = moveX,
		this.moveY = moveY;
	}
	//生成max和min之间的随机数
	function num (max, _min) {
		var min = arguments[1] || 0;
		return Math.floor(Math.random()*(max-min+1)+min);
	}
	// 绘制原点
	function drawCricle (cxt, x, y, r, moveX, moveY) {
		var circle = new Circle(x, y, r, moveX, moveY)
		cxt.beginPath()
		cxt.arc(circle.x, circle.y, circle.r, 0, 2*Math.PI)
		cxt.closePath()
		cxt.fill();
		return circle;
	}
	//绘制线条
	function drawLine (cxt, x, y, _x, _y, o) {
		var line = new Line(x, y, _x, _y, o)
		cxt.beginPath()
		cxt.strokeStyle = 'rgba(0,0,0,'+ o +')'
		cxt.moveTo(line.beginX, line.beginY)
		cxt.lineTo(line.closeX, line.closeY)
		cxt.closePath()
		cxt.stroke();

	}
	//初始化生成原点，这时所有点的初始位置、大小、移动速度、移动方向都确定了
	function init () {
		circleArr = [];
		for (var i = 0; i < POINT; i++) {
      // 这时其实不需要使用drawCircle，因为只需要circle对象
			// circleArr.push(drawCricle(context, num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10)/40, num(10, -10)/40));
      
      // var circle = new Circle(num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10)/40, num(10, -10)/40);
      // circleArr.push(circle);
      
      // 或者手动构造该对象
			circleArr.push({
        x: num(WIDTH), 
        y: num(HEIGHT),
        r: num(15, 2),
        moveX: num(10, -10)/40,
        moveY: num(10, -10)/40
      });
		}
    console.table(circleArr);
		draw();
	}

	//每帧绘制
	function draw () {
		context.clearRect(0,0,canvas.width, canvas.height);
		for (var i = 0; i < POINT; i++) {
			drawCricle(context, circleArr[i].x, circleArr[i].y, circleArr[i].r);
		}
		for (var i = 0; i < POINT; i++) {
			for (var j = 0; j < POINT; j++) {
        // circleArr长度为POINT，所以要判断一下不能越界
				if (i + j < POINT) {
          // 根据两点之间距离确定连线的透明度，越远越透明
					var A = Math.abs(circleArr[i+j].x - circleArr[i].x),
						B = Math.abs(circleArr[i+j].y - circleArr[i].y);
          // 勾三股四，两直角边平方和等于斜边平方和，可得线长度
					var lineLength = Math.sqrt(A*A + B*B);
          // 减去0.009是为了让参数C小于0.009时算出透明度为负的线就不画了
          // 用来控制画线的范围大小
          // 例如：
					// var C = 100/lineLength-0.3;
					var C = 10/lineLength-0.009;
					var lineOpacity = Math.min(C, 0.3);
          // 实际透明度>0的都会画，仔细理解把0.009放在前面的意义
					if (lineOpacity > 0) {
						drawLine(context, circleArr[i].x, circleArr[i].y, circleArr[i+j].x, circleArr[i+j].y, lineOpacity);
					}
				}
			}
		}
	}

	//调用执行
	window.onload = function () {
		init();
    function start() {
			for (var i = 0; i < POINT; i++) {
				var cir = circleArr[i];
				cir.x += cir.moveX;
				cir.y += cir.moveY;
				if (cir.x > WIDTH) cir.x = 0;
				else if (cir.x < 0) cir.x = WIDTH;
				if (cir.y > HEIGHT) cir.y = 0;
				else if (cir.y < 0) cir.y = HEIGHT;
				
			}
			draw();
    	requestAnimationFrame(start);
    }
    requestAnimationFrame(start);
	}

<canvas id="Mycanvas"></canvas>

html,body{
  width:100%;
  height:100%;
  overflow:hidden;
}